This invention relates to a method and apparatus for directly coupling two metallic members such as a shaft and a disc, and more particularly to a method and apparatus for directly coupling two metallic members rotary equipment for enabling a transmitting of large torques.
As a direct coupling method of two metallic members such as a shaft and a disc, there has been proposed a press-in method in which the shaft is pressed into the hollow portion of the disc and so coupled. However, this method has its limits in bonding power and can not be adapted to the application in the field where magnitude of the torque fluctuates drastically. There has been another proposed press-in method in which knurling is in advance applied around the outer circumference of the shaft to increase the bonding power and shaft is then pressed into the hollow portion of the disc. According to this method, however, the hollow portion of the disc and portions nearby tend to be cut off by the crests of knurling or to cause work hardening. Consequently, the disc can not be inserted sufficiently into the knurled portion of the shaft, thereby failing to obtain large shear strength. One disadvantage resides in the fact that, if the portion of the disc near its hollow portion is cut off, it becomes difficult to align the axis of the disc with that of the shaft. Another disadvantage resides in the fact that, if the press force is increased in order to increase the bonding power, the shaft is apt to be bent disadvantageously.